diff --git a/fsw/cfe-core/src/es/cfe_es_start.c b/fsw/cfe-core/src/es/cfe_es_start.c
index 2a883ef13..560fc259d 100644
--- a/fsw/cfe-core/src/es/cfe_es_start.c
+++ b/fsw/cfe-core/src/es/cfe_es_start.c
@@ -494,11 +494,11 @@ void CFE_ES_SetupResetVariables(uint32 StartType, uint32 StartSubtype, uint32 Bo
 */
 void CFE_ES_InitializeFileSystems(uint32 StartType)
 {
-   int32   RetStatus;
-   cpuaddr RamDiskMemoryAddress;
-   uint32  RamDiskMemorySize;
-   int32   BlocksFree;
-   int32   PercentFree;
+   int32        RetStatus;
+   cpuaddr      RamDiskMemoryAddress;
+   uint32       RamDiskMemorySize;
+   int32        PercentFree;
+   OS_statvfs_t StatBuf;
  
    /* 
    ** Get the memory area for the RAM disk 
@@ -601,25 +601,13 @@ void CFE_ES_InitializeFileSystems(uint32 StartType)
       /*
       ** See how many blocks are free in the RAM disk
       */
-      BlocksFree = OS_fsBlocksFree(CFE_PLATFORM_ES_RAM_DISK_MOUNT_STRING);   
-      if ( BlocksFree >= 0 )
+      RetStatus = OS_FileSysStatVolume(CFE_PLATFORM_ES_RAM_DISK_MOUNT_STRING, &StatBuf);
+      if ( RetStatus == OS_SUCCESS && StatBuf.total_blocks > 0 )
       {
-         /*
-         ** Need a sanity check for the desktop systems.
-         ** Because the desktop ports map the volatile disk to the host 
-         ** hard disk, it will report more free blocks than the defined number
-         ** of sectors ( blocks ). Therefore it must be truncated.
-         */
-         if ( BlocksFree > CFE_PLATFORM_ES_RAM_DISK_NUM_SECTORS )
-         {
-             BlocksFree = CFE_PLATFORM_ES_RAM_DISK_NUM_SECTORS - 1;
-         }
-         
          /*
          ** Determine if the disk is too full 
          */
-         BlocksFree = BlocksFree * 100;
-         PercentFree = BlocksFree / CFE_PLATFORM_ES_RAM_DISK_NUM_SECTORS;
+         PercentFree = (StatBuf.blocks_free * 100) / StatBuf.total_blocks;
          CFE_ES_WriteToSysLog("Volatile Disk has %d Percent free space.\n",(int)PercentFree);
 
          if ( PercentFree < CFE_PLATFORM_ES_RAM_DISK_PERCENT_RESERVED )
@@ -721,7 +709,7 @@ void CFE_ES_InitializeFileSystems(uint32 StartType)
       else  /* could not determine free blocks */
       {         
          /* Log error message -- note that BlocksFree returns the error code in this case */
-         CFE_ES_WriteToSysLog("ES Startup: Error Determining Blocks Free on Volume. EC = 0x%08X\n",(unsigned int)BlocksFree);
+         CFE_ES_WriteToSysLog("ES Startup: Error Determining Blocks Free on Volume. EC = 0x%08X\n",(unsigned int)RetStatus);
 
          /*
          ** Delay to allow the message to be read
@@ -983,4 +971,3 @@ int32 CFE_ES_MainTaskSyncDelay(uint32 AppStateId, uint32 TimeOutMilliseconds)
 
     return Status;
 }
-
diff --git a/fsw/cfe-core/unit-test/es_UT.c b/fsw/cfe-core/unit-test/es_UT.c
index 2190e3851..bff84dc8b 100644
--- a/fsw/cfe-core/unit-test/es_UT.c
+++ b/fsw/cfe-core/unit-test/es_UT.c
@@ -711,6 +711,7 @@ void TestStartupErrorPaths(void)
     ES_UT_SetAppStateHook_t StateHook;
     uint32 PanicStatus;
     uint32 ResetType;
+    OS_statvfs_t StatBuf;
     CFE_ES_TaskRecord_t *TaskRecPtr;
     CFE_ES_AppRecord_t *AppRecPtr;
 
@@ -886,6 +887,11 @@ void TestStartupErrorPaths(void)
               "CFE_ES_InitializeFileSystems",
               "Power on reset; error creating volatile (RAM) volume");
 
+    /* prepare the StatBuf to reflect a RAM disk that is 99% full */
+    StatBuf.block_size = 1024;
+    StatBuf.total_blocks = CFE_PLATFORM_ES_RAM_DISK_NUM_SECTORS;
+    StatBuf.blocks_free = CFE_PLATFORM_ES_RAM_DISK_NUM_SECTORS / 100;
+
     /* Test initialization of the file systems specifying a processor reset
      * following a failure to reformat the RAM volume
      */
@@ -893,6 +899,7 @@ void TestStartupErrorPaths(void)
     UT_SetDefaultReturnValue(UT_KEY(OS_initfs), OS_ERROR);
     UT_SetDefaultReturnValue(UT_KEY(OS_mount), OS_ERROR);
     UT_SetDefaultReturnValue(UT_KEY(OS_mkfs), OS_ERROR);
+    UT_SetDataBuffer(UT_KEY(OS_FileSysStatVolume), &StatBuf, sizeof(StatBuf), false);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_INSUFF_FREE_SPACE]) &&
@@ -909,6 +916,7 @@ void TestStartupErrorPaths(void)
      */
     ES_ResetUnitTest();
     UT_SetDefaultReturnValue(UT_KEY(CFE_PSP_GetVolatileDiskMem), CFE_PSP_ERROR);
+    UT_SetDataBuffer(UT_KEY(OS_FileSysStatVolume), &StatBuf, sizeof(StatBuf), false);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_INSUFF_FREE_SPACE]) &&
@@ -916,24 +924,12 @@ void TestStartupErrorPaths(void)
               "CFE_ES_InitializeFileSystems",
               "Processor reset; cannot get memory for volatile disk");
 
-    /* Test initialization of the file systems where the number of free blocks
-     * reported is greater than the number of RAM disk sectors
-     */
-    ES_ResetUnitTest();
-    UT_SetDefaultReturnValue(UT_KEY(OS_mount), OS_ERROR);
-    UT_SetDeferredRetcode(UT_KEY(OS_fsBlocksFree), 1, CFE_PLATFORM_ES_RAM_DISK_NUM_SECTORS + 1);
-    CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
-    UT_Report(__FILE__, __LINE__,
-              UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_MOUNT_VOLATILE]) &&
-                UT_GetStubCount(UT_KEY(OS_printf)) == 2,
-              "CFE_ES_InitializeFileSystems",
-              "Processor reset; truncate free block count");
-
     /* Test initialization of the file systems specifying a processor reset
      * following a failure to remove the RAM volume
      */
     ES_ResetUnitTest();
     UT_SetDefaultReturnValue(UT_KEY(OS_rmfs), OS_ERROR);
+    UT_SetDataBuffer(UT_KEY(OS_FileSysStatVolume), &StatBuf, sizeof(StatBuf), false);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_INSUFF_FREE_SPACE]) &&
@@ -947,6 +943,7 @@ void TestStartupErrorPaths(void)
      */
     ES_ResetUnitTest();
     UT_SetDeferredRetcode(UT_KEY(OS_unmount), 1, -1);
+    UT_SetDataBuffer(UT_KEY(OS_FileSysStatVolume), &StatBuf, sizeof(StatBuf), false);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_INSUFF_FREE_SPACE]) &&
@@ -968,6 +965,7 @@ void TestStartupErrorPaths(void)
      */
     ES_ResetUnitTest();
     UT_SetDefaultReturnValue(UT_KEY(OS_mount), OS_ERROR);
+    UT_SetDataBuffer(UT_KEY(OS_FileSysStatVolume), &StatBuf, sizeof(StatBuf), false);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_INSUFF_FREE_SPACE]) &&
@@ -981,7 +979,7 @@ void TestStartupErrorPaths(void)
      * number of blocks that are free on the volume
      */
     ES_ResetUnitTest();
-    UT_SetDeferredRetcode(UT_KEY(OS_fsBlocksFree), 1, -1);
+    UT_SetDeferredRetcode(UT_KEY(OS_FileSysStatVolume), 1, -1);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_DETERMINE_BLOCKS]) &&
@@ -1106,6 +1104,7 @@ void TestStartupErrorPaths(void)
     ES_ResetUnitTest();
     UT_SetDefaultReturnValue(UT_KEY(OS_initfs), OS_ERROR);
     UT_SetDefaultReturnValue(UT_KEY(OS_mount), OS_ERROR);
+    UT_SetDataBuffer(UT_KEY(OS_FileSysStatVolume), &StatBuf, sizeof(StatBuf), false);
     CFE_ES_InitializeFileSystems(CFE_PSP_RST_TYPE_PROCESSOR);
     UT_Report(__FILE__, __LINE__,
               UT_PrintfIsInHistory(UT_OSP_MESSAGES[UT_OSP_INSUFF_FREE_SPACE]) &&